I believe it is a few things. Light finger to get single shots versus repeated. First few shots to figure out how bad the sights are. Shoot around the star until you have a good perimeter. Shoot the center to pop it out.
Though you can find credible marksmen that know all this, yet fail to win. It's rigged.
It is rigged, but it's the paper targets (star diagram). The paper intentionally is strong enough that it is highly improbable that any bb/pellet gun will have the force to knock out the remaining 20% of the outline of the star no matter how accurate the shooter is. The inner part of the target will begin to fold on purpose.